Velocity variation transmitterreceiver



Nov. 30, 1948. SAMUEL 2,455,094

VELOCITY VARIATION TRANSMITTER-RECEIVER Filed June 28, 1941 momurlolv /NVENTOR ALSAMUEL VWW ATTORNEY Patented Nov. 30, I948 VELOCITY VARIATION TRANSMITTER- RECEIVER.

Arthur L. Samuel Su N- J i n r to Be l Telephone Laboratories, Incorporated,

New

York, N. Y., a corporation of New York Applicationdune 28, 1941-, Serial No. 400,279

4' Claims. 1

This invention relates to apparatus for com-. munication by means of ultra-high frequency electromagnetic Waves, and more particularly to a combined transmitter and receiver for duplex operation.

The invention further relates to equipment for lineeoflsight communication. It employs a vacuum tube utilizing electron velocity variations in conjunction with a hollow resonating chamber and a radiating Wave guide.

Among the objects of the invention are to make the apparatus compact, readily portable and simple to operate and maintain.

A specific object is to employ the same vacuum tube both in transmitting and receiving. Other specific objects are to avoid the necessity for employing a quenching oscillator to disable the transmitter while receiving and at the same time to avoid switching of high frequency connections between the transmitter and receiving conditions.

A feature is a direct coupling between a resonant cavity and a directive antenna of the slotted Wave guide type.

Another feature lies in varying the feedback in a velocity variation system by varying the transit time of the electrons in the drift space.

The invention is more fully described hereinafter byan illustrative example with reference to the accompanying drawing in which:

Fig; 1 is a perspective View of a combined transmitter and receiver, shown partly broken away; and partly diagrammatically;

Fig. 1A is an alternative circuit diagram for substitution in Fig. 1;

Fig. 2 is a fragmentary View of the apparatus showing certain structural details; and

Fig. 3 is a plan view on a reduced scale.

Referring to the figures, ill represents a vacuum tube containing a series of electrodes I i, i2, i3 and M to two of which, [2 .and i3, is conductively attached an inner cylindrical casing and to the other two, ii and ii, an outer cylindrical casing it, the two casings being conductively joined by a rod or wire 51. The outer casing I6 is provided with a pair of slots l8 and I8, shown in Fig. 2 A pair of rectangular wave guides l9 and are mounted at the sides of the casing i6 and, if desired, may be arranged to permit a certain amount of rotation about the axis of the tube H]. The guides i9 and 2B are each open at the end adjace t the casing 56 so that the interiors of the guides communicate with the interior of the casing i6 through. the respective slots l8 and 68'. Th other end of ea h of the uid is sh n o n but it may be los d if desi scl- The gu de 9 is provided w th-a ngitudinal slot 21 an th gu d 29 wi hv a s milar longitudi al lo 2 h uid s I 3 and 20 prefe a l set apart at a Wi e angl 20 as sh wn inFi 3., th al e o a i d pen en up th physica dimensi ns of t e Wa u e t iv the be efliciehc of ra ia n f om the de ice a di ecti te na.

he vacuum t s 89 a be fth ty e sho n in Fi 3 fmy ap lica ion S ial Ito- 375. 1 filed anuary 21. 1.9% l, n assi ed. o the as shs Of th resen app icati n. is u d s aten o- 22811117. M y 5. .1 2- A suitabl lectron u is m unt d at th l wer end f th t be it and tompris sa cathode 2. a d a acce erati elec r d 24 brousht u throu h. le ds 5 an re ectivsi The c tho e may be heated i hy suitle Ihehh l? aai exampl b a terna n cu ent appl ed hr ugh a t a s o mer 3 a leads Z8. and 23. o hich l ad 29 ay be conne ted to lsa fi The electrode ii. i2, is and is may be t' he ty d sslosed inmy above-m t n pnl seti lectr des 2 and t be n conouct ve y conn c e w t t e inn ca n I i and l ctr des H n l Wit th outer cas 1 n ele t o ollec in electrode 0 collec r $9 is r v d d t he upper end of t e be v 1 The asings wand 15 may be oun ed b m ans o a lead 3! o othe is con ed th the gr unded P si ve term na of a o r 3 e ss s h ive f r e The n gative term nal o the s urce 3. connect d to th c t o e b means of eads 3 and ther au i iar s incl d a telep one transi r 34 ohh ctsd' n c nv ntiona manne to th grid. of a low fre ue cy ampl fi r 5: A m pole switch 36, shown designed for manual operation but hich may be electrically operated, if ded. s pr id o swi ch the l f equen y onnec ion o the sys em. b we n h sm tis and re iv g ditio s Th s t h is w in he re v n c it on ln his osit o the p er arm 3'? of e sw h onnect t collector i i' ith t e cathod b Wa o the onda y Wind ng of s ansform r 0-, Th mid e arm hi h ch 3 o ne t the ascelerating electrodedd by an obvious path to the mor n at e scn st of a o nti m ter 43 acros the sourc 32 Th lower ar 44 o th w c t nnects t e p t o he am lifier 15 with e al of a le hon ce er 450 th transi f ev ce.- Th msih heterh ins o the re e ve; 2 is ssh s to he more n si- -i e c n c ie t e hst n ms er 43.

In the transmitting or lower position of the w ch it the s itch srm i connec s th s llss 30 to ground potential, the arm 4! connects the accelerating electrode to the potentiometer contact 46 through a series resistor 41, and the lower arm 44 connects the plate of the tube 35 to the accelerating electrode.

In the operation of the system for transmitting, with the switch 36 in the lower position, the full potential difierence of the source 32 is applied between the cathode 23 and the collector 30 of the tube H). In this position of the switch the accelerating electrode 24 is placed at an intermediate potential and coupled to the plate of the low frequency amplifier 35. The collector 30 is at the same potential as the walls of the resonating chamber and the electrodes ll, l2, l3 and I4. The tube in operates as an ultra-high frequency oscillator employing the electron velocity variation principle. A beam of electrons projected by the electron gun is subjected to a velocity variation in passing through the gap between the electrodes H and I2 due to reaction with electromagnetic oscillations in the interior of the resonating chamber. The velocity variations of the beam are converted into electron charge density variations during the time required for the electrons to drift to the gap between the electrodes l3 and I4. The charge density-varied electron beam yields part of its kinetic energy to the electromagnetic field at this point, provided the electron transit time has been properly adjusted with respect to the resonant frequency of the chamber. The electromagnetic field in the chamber is maintained in sustained oscillations by the energy so contributed by the electron beam, in well-known manner. After passing the gap between electrodes l3 and [4 the electron beam is intercepted by the collector 30. A portion of the energy of the oscillating electromagnetic field escapes from the resonating chamber through the slots 18 and I8 and produces traveling waves in the guides 19 and 20. Radiation from the slots 2| and 22 occurs primarily in the plane of the slots and is directed in the direction of the bisector of the angle between the guides l9 and 20. The ultrahigh frequency output of the system is amplitudemodulated by signals from the telephone transmitter 34 impressed upon the accelerating electrode 24 in amplified form from the plate circuit of the tube 35. The signal-varied plate potential of the tube 35 impresses corresponding potential variations upon the accelerating electrode 24, thus varying the beam current and consequently varying the power output of the oscillator. Additional audio amplification may be employed if necessary by adding additional stages.

In the operation of the system of Fig. 1 as a receiver the switch 35 is placed in the upper position. Three changes are effected by the switching. The middle switch arm 4| transfers the accelerating electrode 24 to a reduced voltage, thereby reducing the beam current, preferably to a value insufiicient to produce sustained oscillations but providing a controllable amount of regeneration, if desired. The upper switch arm 3'! transfers the collector to a reduced voltage in the neighborhood of the cathode potential, thereby setting up an electron retarding or reflecting field between the electrode I4 and the collector 30. The lower switch arm 44 transfers the plate of the low frequency amplifier to the telephone receiver 45 with a somewhat increased plate potential due to elimination of the series resistor 41 from the circuit.

The incoming ultra-high frequency wave intercepted by the slotted guides l9 and 20 is directed into the resonating chamber through the slots l8 and I8, setting up standing waves in the chamber. The waves in the chamber serve to effect velocity variation of the electron beam at both gaps within the cavity of the chamber. The velocity variation at the first gap is converted into an electron current density variation by transit time grouping in the drift space in the usual manner so that the drift electrons are enabled to deliver power to the electromagnetic field in the chamber by reaction at the second gap. Because of the reduced beam current the power supplied to the field by the beam will be insufficient to produce sustained oscillations when properly adjusted for receiving. As above mentioned, a controllable amount of regeneration may be employed by adjusting the strength of the beam current. Detection will occur in the collector circuit due to the action of the retarding field which is set up by having the collector at a potentia1 in the neighborhood of the cathode potential. The electrons after passing the gap between the electrodes l3 and M will still have sufficient velocity variations so that electron sorting takes place in the retarding field in accordance with the velocities of the individual electrons. The slower electrons are turned back before reaching the collector. The number of electrons which gain sufiicient momentum to reach the collector depends upon the amount of velocity variation which has been imparted to the beam by the incoming signal. Accordingly, the stronger the signal the more electrons will reach the collector per unit of time and the greater the detected current delivered to the translator 45.

An alternative method of controlling the regeneration in the receiving condition consists in changing the electron transit time in the drift space by an adustment of the direct current potential difference between the cathode and the resonating chamber so that the current variation at the second gap is nearly in quadrature with respect to the electromagnetic field effective across this gap. The quadrature relationship may be secured by changing the voltage a small amount so that the transit time is equal to an integral number of cycles of the field oscillations. The velocity variation efiects produced at the two gaps by the incoming signal will in this case be additive and hence detection is possible in the same manner as before. A slight increase in the voltage with respect to the condition of quadrature will produce regeneration whereas a decrease will produce degeneration. The condition for sustained oscillations requires a transit time of n+%) cycles as explained in connection with an oscillator disclosed in U. S. patent application Serial No. 386,794, filed April 4, 1941, by A. E. Anderson and A. L. Samuel, issued as Patent No. 2,405,175, August 6, 1946, and assigned to the same assignee. In accordance with the explanation given in the Anderson-Samuel application it will be evident that the condition for degeneration requires a transit time of (ml- A1) cycles and a transit timeof n cycles corresponds to a condition in which the electron beam neither contributes energy to the field nor abstracts energy therefrom.

The alternative method of operation above referred to may be incorporated into the switching arrangements by a slight modification of the connections to the switch 36 as shown in Fig. 1A. In this method of operation no change in the beam current is required, hence the accelerator potential need not be changed and lead 48 may be permanently connected to the slider 42. The connections to the middle switch arm M are changed as indicated in Fig. 1A where the designation of the switch arm has been changed to ll. The cathode lead 50 is connected to the switch arm 4| so that the cathode potential may be changed by a small amount in switching between the transmitting and receiving conditions. For this purpose the additional potentiometer sliders 5| and 52 are provided and connected to the terminals associated with the switch arm ll. The contacts 5| and 52 may be adjusted to give regeneration, degeneration or a neutral condition as explained above.

If desired, the two methods of reaction control shown respectively in Fig. 1 and Fig. 1A may be used simultaneously. Which of the methods, or what sort of a combination of the two, will ce preferable in a given case may best be determined by experiment.

The directional antenna array illustrated comprises two rectangular wave guides mounted at an angle with respect to each other. The guides are provided with radiating slots H and 22 on their opposing faces. Other suitable guides having circular or various other cross sections may be employed, if desired, in place of rectangular guides. Radiating slots of a variety of forms might be used. With the optimum adjustment of the size of the radiating slot, and of the angle between the wave guides, the system provides a high degree of directivity, the transmission being principally confined to the plane of the slots and. distributed about equally well in all directions in this plane within the angle between the guides. The antenna array is particularly adapted for use with the plane vertical in which case there is selective transmission in a desired azimuthal direction broadly scattered over a considerable range of elevations. At the receiving point the plane of the receiving antenna may be adjusted in the proper direction for best reception without imposing stringent requirements on the adjustment of the elevation.

The resonating chamber may be coupled to the antenna array in various suitable ways as, for example, by means of a slot, iris, coupling loop, etc-., all of which are well known per se. For operation at a predetermined single frequency the angle between the two guides as well as the size of the coupling aperture may be fixed with an adjustment for tuning the resonant cavity as by means of a micrometer screw or the like, if desired.

What is claimed is:

1. Combined transmitting and receiving apparatus comprising: a resonating chamber for ultra-high frequency waves; an electron discharge device including a cathode for supplying an electron stream, and, in succession along the path of said electron stream, an accelerating electrode, a plurality of electrodes integral with said resonating chamber, defining input and output gaps separated by a substantially field-free drift space, and a collecting electrode; means operative while transmitting to maintain said accelerating and collecting electrodes respectively at relatively high positive potentials with respect to said cathode, whereby electromagnetic oscillations are sustained in said resonating chamber; means operative while receiving to maintain said accelerating electrode at a reduced positive potential, whereby the tube and chamber are enabled to function as a regenerative amplifier, and to maintain said collecting electrode at substantially cathode potential, whereby the tube is enabled to function as a detector of velocity variations in the electron stream.

2. The combination of claim 1 with the addition of means for switching the system to either the transmitting or the receiving condition.

3. Combined transmitting and receiving apparatus comprising an electron beam tube including a cathode, an accelerating electrode, and a collecting electrode, an associated resonating chamber, means within said chamber defining an input gap and an output gap traversed by the electron beam of said tube, means defining a substantially field-free drift space between said input and output gaps. means operative while transmitting to maintain said acceleratingand collecting electrodes respectively at relatively high positive potentials with respect to said cathode, whereby V electromagnetic oscillations are sustained in said REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,206,923 Southworth July 9, 1940 2,235,010 Chaffee Mar. 18, 1941 2,259,690 Hansen et al Oct. 21, 1941 OTHER REFERENCES Varian and Varian, Journal of Applied Physics, vol. 10, May 1939, pp. 321-327. 

